My uncle & aunt in Canada applied for their OAS (Old age security) & GIS (Guaranteed Income Supplement) & Allowance payments in January 2017 and they were qualified to receive all benefits from January 2017. This kind of application usually gets processed in 6 months and the applicant usually starts receiving monthly payments in 6 months (processing time) + lumpsum retroactive payment for processing time.
What happened in our case is the application got delayed for some query and it got approved at the end of 2019 and all payments from 2017, 2018 & 2019 were received as one big lump sum payment in 2019 and eventually one Tax Slip - T4 for 2019 which included payments from 2017, 2018 & 2019.
I'm helping my uncle & aunt with their taxes. What I realized is if they had lower income in 2019 T4 slips. They would have qualified for much higher "Refundable Tax Credits" such as Trillium benefit (Ontario Sales Tax Credit, Ontario Energy and Property Tax Credit, Ontario Senior Homeowners’ Property Tax Grant), etc.
They'll lose roughly $2,100 this year in terms of refundable credit compared to they were only paid their 2019 benefits in 2019 instead of all lumpsum from the previous year as well.
What options do we have here? Can we request individual T4s for each year and refile their taxes for 2017, 2018?